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zunmbr.f(3) LAPACK zunmbr.f(3)

zunmbr.f -


subroutine zunmbr (VECT, SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC, WORK, LWORK, INFO)
 
ZUNMBR

ZUNMBR
Purpose:
 If VECT = 'Q', ZUNMBR overwrites the general complex M-by-N matrix C
 with
                 SIDE = 'L'     SIDE = 'R'
 TRANS = 'N':      Q * C          C * Q
 TRANS = 'C':      Q**H * C       C * Q**H
If VECT = 'P', ZUNMBR overwrites the general complex M-by-N matrix C with SIDE = 'L' SIDE = 'R' TRANS = 'N': P * C C * P TRANS = 'C': P**H * C C * P**H
Here Q and P**H are the unitary matrices determined by ZGEBRD when reducing a complex matrix A to bidiagonal form: A = Q * B * P**H. Q and P**H are defined as products of elementary reflectors H(i) and G(i) respectively.
Let nq = m if SIDE = 'L' and nq = n if SIDE = 'R'. Thus nq is the order of the unitary matrix Q or P**H that is applied.
If VECT = 'Q', A is assumed to have been an NQ-by-K matrix: if nq >= k, Q = H(1) H(2) . . . H(k); if nq < k, Q = H(1) H(2) . . . H(nq-1).
If VECT = 'P', A is assumed to have been a K-by-NQ matrix: if k < nq, P = G(1) G(2) . . . G(k); if k >= nq, P = G(1) G(2) . . . G(nq-1).
Parameters:
VECT
          VECT is CHARACTER*1
          = 'Q': apply Q or Q**H;
          = 'P': apply P or P**H.
SIDE
          SIDE is CHARACTER*1
          = 'L': apply Q, Q**H, P or P**H from the Left;
          = 'R': apply Q, Q**H, P or P**H from the Right.
TRANS
          TRANS is CHARACTER*1
          = 'N':  No transpose, apply Q or P;
          = 'C':  Conjugate transpose, apply Q**H or P**H.
M
          M is INTEGER
          The number of rows of the matrix C. M >= 0.
N
          N is INTEGER
          The number of columns of the matrix C. N >= 0.
K
          K is INTEGER
          If VECT = 'Q', the number of columns in the original
          matrix reduced by ZGEBRD.
          If VECT = 'P', the number of rows in the original
          matrix reduced by ZGEBRD.
          K >= 0.
A
          A is COMPLEX*16 array, dimension
                                (LDA,min(nq,K)) if VECT = 'Q'
                                (LDA,nq)        if VECT = 'P'
          The vectors which define the elementary reflectors H(i) and
          G(i), whose products determine the matrices Q and P, as
          returned by ZGEBRD.
LDA
          LDA is INTEGER
          The leading dimension of the array A.
          If VECT = 'Q', LDA >= max(1,nq);
          if VECT = 'P', LDA >= max(1,min(nq,K)).
TAU
          TAU is COMPLEX*16 array, dimension (min(nq,K))
          TAU(i) must contain the scalar factor of the elementary
          reflector H(i) or G(i) which determines Q or P, as returned
          by ZGEBRD in the array argument TAUQ or TAUP.
C
          C is COMPLEX*16 array, dimension (LDC,N)
          On entry, the M-by-N matrix C.
          On exit, C is overwritten by Q*C or Q**H*C or C*Q**H or C*Q
          or P*C or P**H*C or C*P or C*P**H.
LDC
          LDC is INTEGER
          The leading dimension of the array C. LDC >= max(1,M).
WORK
          WORK is COMPLEX*16 array, dimension (MAX(1,LWORK))
          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
LWORK
          LWORK is INTEGER
          The dimension of the array WORK.
          If SIDE = 'L', LWORK >= max(1,N);
          if SIDE = 'R', LWORK >= max(1,M);
          if N = 0 or M = 0, LWORK >= 1.
          For optimum performance LWORK >= max(1,N*NB) if SIDE = 'L',
          and LWORK >= max(1,M*NB) if SIDE = 'R', where NB is the
          optimal blocksize. (NB = 0 if M = 0 or N = 0.)
If LWORK = -1, then a workspace query is assumed; the routine only calculates the optimal size of the WORK array, returns this value as the first entry of the WORK array, and no error message related to LWORK is issued by XERBLA.
INFO
          INFO is INTEGER
          = 0:  successful exit
          < 0:  if INFO = -i, the i-th argument had an illegal value
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
November 2011
Definition at line 196 of file zunmbr.f.

Generated automatically by Doxygen for LAPACK from the source code.
Sat Nov 16 2013 Version 3.4.2

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